Hypertrophic scarring and keloid formation are serious derangements in healing defined largely on the basis of an abnormal accumulation and arrangement of extracellular matrix. This project asks a simple question: Do fibroblasts from normal scar tissue and from hypertrophic (or keloid) scar tissue differ in the way they process (degrade) extracellular matrix? It will address the dynamics of extracellular matrix metabolism in reparative tissues and will establish if (and how) fibroblastic degradation of glycosaminoglycan (primarily hyaluronate) differs between normal skin, normal mature scar, and hypertrophic/keloid scar tissue. The specific aims will be to: 1. Introduce radiolabeled glycosaminoglycan substrate to fibroblasts derived from normal mature scars and hypertrophic scars (as well as from other reparative tissues) and observe how the labeled matrix substrate is internalized by cells. 2. Determine if the affinity or capacity for internalizing substrate differs between normal and hypertrophic scar fibroblasts (since such a difference could explain the formation of excess matrix seen in abnormal scarring). 3. Establish how and where the internalized substrate is degraded within cells. 4. Learn whether depolymerized substrate (in the form of labeled monosaccharides, disaccharides or oligosaccharides) are salvaged and reused in synthesizing new glycosaminoglycan or other N-acetylhexosamine-containing substances. Previous work in our laboratory has shown that hyaluronidase resides within wound fibroblasts and functions entirely intracellularly; this project will compare the stated cell types in terms of the way they accomplish matrix internalization, degradation, and re-synthesis/secretion since such processes are likely to be key differences in the behavior of normal scar and hypertrophic scar cells. Explant-derived fibroblasts from both human and animal (rabbit) tissues will be cultured. In the case of human tissues, cells will be obtained from samples of normal skin, of normal (mature) scar and of hypertrophic/keloid scar. Analytical procedures will include determining binding of [3H]-hyaluronate to fibroblasts, measuring [3H]-hyaluronate internalization, accumulation and degradation within fibroblasts, identifying (by cellular disruption/density gradient centrifugation) the subcellular location(s) of labeled hyaluronate-derived digestion products and then correlating these sites with the hyaluronidase activities of corresponding subcellular fractions.